package multi_thread;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class Mutex implements Lock, Serializable {

    private static class Sync extends AbstractQueuedSynchronizer{
        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        @Override
        protected boolean tryAcquire(int arg) {
            assert arg == 1;
            if(compareAndSetState(0,1)){
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        @Override
        protected boolean tryRelease(int arg) {
            assert arg == 1;
            if(getState() == 0){
                setExclusiveOwnerThread(null);
            }
            setState(0);
            return true;
        }

        Condition newCondition(){
            return new ConditionObject();
        }

        private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {
            s.defaultReadObject();
            setState(0);
        }
    }

    private final Sync sync = new Sync();
    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);

    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.release(1);

    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }

    public boolean hasQueueThreads(){
        return sync.isHeldExclusively();
    }

    private static Mutex mutex = new Mutex();

    public static void main(String[] args) {
        for (int i = 0; i < 10; i++) {
           Thread thread = new Thread(()->{
               mutex.lock();
               try{
                   Thread.sleep(1000);
               }catch (InterruptedException e){
                   e.printStackTrace();
               }finally {
                   mutex.unlock();
               }
           });
           thread.start();
        }
    }
}
